Events

Understand events and event emitters in Tensei

Tensei ships with an event emitter based on the emittery library. The most popular use cases for events and listeners is performing actions after operations are completed in the application. For example, after a user is registered, a user::registered event is emitted.

Emitting events

To emit a new event, you may use the emittery instance from the context (or request) instance. Let's say you have a route that deletes a user account:

const { tensei, route } = require('@tensei/core')

tensei()
    .routes([
        route('Delete customer account')
            .handle(async ({ emitter, manager, params }, response) => {
                await manager.remove('Customer', params.id)

                emitter.emit('customer::deleted', params.id)

                return response.noContent()
            })
    ])

Many plugins that add custom routes and graphql queries will emit events after actions are performed.

Listening to events

To listen to events, you may use the .events() method on the tensei instance.

const { tensei, route, event } = require('@tensei/core')

tensei()
    .events([
        event('customer::deleted')
            .listen(async ({ payload, ctx }) => {
                ctx.mailer.send((message) => message.to(payload.email))
            })
            .listen(async ({ payload, ctx }) => {
                ctx.manager.update('Customer', {...}, {...})
            })
    ])

You may register as many event listeners as possible to one event. All of these listeners will be called asynchronously when the event is triggered.

Listening to events in plugins

If you are building a plugin, you may use the extendEvents method to add event listeners:

const { plugin, event } = require('@tensei/common')

plugin('Manager Users')
    .boot(({ extendEvents }) => {
        extendEvents([
            event('user::registered')
                .listen(async ({ payload }) => {...})
        ])
    })